US5351324A - Fiber optic security seal including plural Bragg gratings - Google Patents

Fiber optic security seal including plural Bragg gratings Download PDF

Info

Publication number
US5351324A
US5351324A US08120113 US12011393A US5351324A US 5351324 A US5351324 A US 5351324A US 08120113 US08120113 US 08120113 US 12011393 A US12011393 A US 12011393A US 5351324 A US5351324 A US 5351324A
Authority
US
Grant status
Grant
Patent type
Prior art keywords
fiber
light
invention
optical
gratings
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
US08120113
Inventor
Peter R. Forman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Los Alamos National Security LLC
Original Assignee
University of California
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Grant date

Links

Images

Classifications

    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09FDISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F3/00Labels, tag tickets, or similar identification or indication means; Seals; Postage or like stamps
    • G09F3/02Forms or constructions
    • G09F3/03Forms or constructions of security seals
    • G09F3/0376Forms or constructions of security seals using a special technique to detect tampering, e.g. by ultrasonic or optical means

Abstract

An optical security system enables the integrity of a container seal to be remotely interrogated. A plurality of Bragg gratings is written holographically into the core of at least one optical fiber placed about the container seal, where each Bragg grating has a predetermined location and a known frequency for reflecting incident light. A time domain reflectometer is provided with a variable frequency light output that corresponds to the reflecting frequencies of the Bragg gratings to output a signal that is functionally related to the location and reflecting frequency of each of the Bragg gratings.

Description

This invention relates to optical fibers with induced Bragg gratings and, in particular, to optical fibers with induced Bragg gratings forming a security pattern. This invention was made with government support under Contract No. W-7405-ENG-36 awarded by the U.S. Department of Energy. The government has certain rights in the invention.

BACKGROUND OF INVENTION

There are a variety of applications where security must be assured and where such security must be ascertained from a location remote from the secured object. Older, prior art security seals were formed from metal tapes for electrical current continuity, embossed devices that were destroyed if the seal integrity was compromised, and other clasps and loops with identifiable impressions. Such devices can readily be counterfeited and/or defeated.

U.S. Pat. No. 3,854,792, issued Dec. 17, 1974, overcomes many of the problems of the prior art by using a fiber optic bundle wherein security masks provide light transmission security patterns between an input end of the fiber bundle and an output end of the bundle. The device requires, however, sufficient space to accommodate a bundle of fibers and access to both ends of the bundle to verify the optical transmission of the bundle.

These problems are addressed by the present invention and an improved fiber optic seal device is provided. Accordingly, it is an object of the present invention to provide a fiber optic seal security system that does not require access to both ends of an optical fiber for security interrogation.

Another object of the present invention is to provide a fiber optic seal device that requires only a few optical fibers, and preferably only one optical fiber, to provide the information needed to verify seal security. Additional objects, advantages and novel features of the invention will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

SUMMARY OF THE INVENTION

To achieve the foregoing and other objects, and in accordance with the purposes of the present invention, as embodied and broadly described herein, the method/apparatus of this invention may comprise a fiber optic seal security system. At least one optical fiber has a plurality of Bragg gratings written holographically into the core of the fiber, where each Bragg grating has a predetermined location and a known frequency for reflecting incident light. A time domain reflectometer, having a variable frequency light output that corresponds to the reflecting frequencies of the Bragg gratings, receives reflected light and outputs a signal that is functionally related to the location and reflecting frequency of each of the Bragg gratings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the embodiments of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:

FIG. 1 is a pictorial illustration and block diagram of an optical fiber seal device according to the present invention.

FIG. 2 graphically illustrates an output from a time domain interferometer having three induced spaced-apart Bragg gratings.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring first to FIG. 1, there is shown a pictorial illustration of one embodiment of a fiber optic seal device according to the present invention. A sealed container 10 is illustrated with a sealed closure 12 whose integrity must be monitored. It will be appreciated that the fiber optic seal described herein may be used with a plurality of devices and may monitor a variety of conditions associated with storage integrity.

An optical fiber 14, which may be doped with, e.g., germanium, is located functionally about container 10 so that fiber 14 will be broken or distorted if the integrity of container 10 is broken or disturbed. Optical fiber 14 defines a plurality of Bragg gratings, e.g., gratings 16, 18, 22, written onto the core of fiber 14, at discrete locations along the length of fiber 14. Each Bragg grating is formed by transverse irradiation of the core of an optical fiber with a particular wavelength of light in the ultraviolet absorption band of the core material. The core is illuminated from the side with two coplanar, coherent beams incident at selected and complementary angles with respect to the axis of the core. The grating period is selected by varying the beam angles of incidence. The resulting interference pattern induces a permanent change in the refractive index of the core material to create a phase grating effective for affecting light in the core at selected wavelengths. The procedure for inducing the Bragg gratings is fully described in U.S. Pat. No. 4,725,110, incorporated herein by reference.

Each Bragg grating 16, 18, 22 now reflects a specific wavelength of light. The magnitude of this reflectivity can be about 90% and the wavelength of reflectivity is determined at the time of exposure to the UV light. Thus, the pattern of reflectivities, i.e., the location and reflected wavelength of each grating, forms a security code that can be interrogated from either end of optical fiber 14.

To interrogate the security code, a light source 24 is directed through beam splitter 26 and lens 28 into optical fiber 14. Light source 24 is preferably a coherent light source that can be varied over the range of Bragg grating reflective wavelengths. Light reflected from gratings 16, 18, and 22 is directed by beam splitter 26 onto a conventional time domain reflectometer. A suitable reflectometer 32 is available from Opto-Electronics, modified to use output laser diodes corresponding to the Bragg grating reflective wavelengths. Reflectometer 32 is locked to light source 24 so that reflectometer 32 outputs a signal indicative of both frequency and time, i.e., the grating reflective wavelength and position along fiber 14.

FIG. 2 graphically depicts the reflection pattern from an optical fiber having induced gratings according to the present invention. An optical fiber 80 microns in diameter with an elliptical core 1.5×2.5 microns was induced with gratings having reflectivities at wavelengths of 830, 833, and 835 nm. The fiber was a single mode fiber that maintains polarization for the incident light. FIG. 2 shows the reflections from the gratings at the selected wavelengths. A time domain reflectometer 32 (FIG. 1) further provides an output signal functionally related to the location of each reflective frequency along the fiber. While the fiber could be broken and refused, a detectable reflection at the resulting joint would appear in the reflection pattern. Likewise, if the fiber is highly strained, the reflected wavelengths would be altered as the grating is elongated.

As discussed above, after the gratings are selectively induced in the fiber, the fiber is attached around the container to be sealed in such a manner that the fiber would be broken or severely distorted if the container were opened. A single fiber might be used to seal several containers where the security code also identifies each particular container. One end of the fiber is sealed within a container and the other end is placed in a location accessible to the interrogation system. In a preferred embodiment, the extending end of the fiber is fitted with a connecting device for quick connection to the interrogation system.

Another security feature might be incorporated onto the optical fibers to verify the identity of the fiber being interrogated. In one embodiment, the extending end of the fiber 14 (see FIG. 1) is coated with a rapid crystallizing material, e.g., a copper sulfate solution or sugar solution, that forms a random pattern of crystals over the face of the connector. This pattern is recorded with holographic interferometry or surface profiling for future comparison. Thereafter, the pattern is verified before the fiber is interrogated. The crystal pattern would be destroyed each time the seal is interrogated and a new coating would be applied as the security coating.

The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.

Claims (2)

What is claimed is:
1. A fiber optic security seal system, comprising:
an optical fiber having a plurality of reflective Bragg gratings induced in the fiber, where each grating has a unique location and wavelength for reflecting incident light;
a light source means for providing input light to said fiber at all of said wavelengths for reflecting light from said gratings;
a time domain reflectometer for receiving reflected light from said gratings and outputting a signal functionally related to said unique location and wavelength for reflecting incident light for each said grating; and
a coating over an end of said optical fiber receiving said incident light said coating having a crystal pattern that produces a unique holographic image to verify an identity of said optical fiber.
2. A fiber optic security seal system according to claim 1, wherein said optical fiber has a core doped with germanium.
US08120113 1993-09-10 1993-09-10 Fiber optic security seal including plural Bragg gratings Expired - Fee Related US5351324A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US08120113 US5351324A (en) 1993-09-10 1993-09-10 Fiber optic security seal including plural Bragg gratings

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US08120113 US5351324A (en) 1993-09-10 1993-09-10 Fiber optic security seal including plural Bragg gratings

Publications (1)

Publication Number Publication Date
US5351324A true US5351324A (en) 1994-09-27

Family

ID=22388343

Family Applications (1)

Application Number Title Priority Date Filing Date
US08120113 Expired - Fee Related US5351324A (en) 1993-09-10 1993-09-10 Fiber optic security seal including plural Bragg gratings

Country Status (1)

Country Link
US (1) US5351324A (en)

Cited By (32)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5416866A (en) * 1992-08-26 1995-05-16 Telefonaktiebolaget L M Ericsson Optical waveguide/grating device for filtering optical wavelengths
US5457760A (en) * 1994-05-06 1995-10-10 At&T Ipm Corp. Wavelength division optical multiplexing elements
US5471551A (en) * 1991-12-24 1995-11-28 Robert Bosch Gmbh Component for use in the transmission of optical signals
US5475780A (en) * 1993-06-17 1995-12-12 At&T Corp. Optical waveguiding component comprising a band-pass filter
US5493113A (en) * 1994-11-29 1996-02-20 United Technologies Corporation Highly sensitive optical fiber cavity coating removal detection
WO1996017223A1 (en) * 1994-11-29 1996-06-06 United Technologies Corporation Optical fiber bragg grating coating removal detection
WO1996031022A1 (en) * 1995-03-27 1996-10-03 Bicc Public Limited Company Optical fibre and network
US5625472A (en) * 1992-12-23 1997-04-29 Lucent Technologies Inc. Method for forming distributed Bragg reflectors in optical media
US5633975A (en) * 1995-11-14 1997-05-27 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Security system responsive to optical fiber having Bragg grating
US5760391A (en) * 1996-07-17 1998-06-02 Mechanical Technology, Inc. Passive optical wavelength analyzer with a passive nonuniform optical grating
US5838851A (en) * 1996-06-24 1998-11-17 Trw Inc. Optical-loop signal processing using reflection mechanisms
US5852687A (en) * 1997-07-09 1998-12-22 Trw Inc. Integrated optical time delay unit
US5892860A (en) * 1997-01-21 1999-04-06 Cidra Corporation Multi-parameter fiber optic sensor for use in harsh environments
US5997140A (en) * 1997-12-29 1999-12-07 Novartis Ag Actively controllable multifocal lens
US6016702A (en) * 1997-09-08 2000-01-25 Cidra Corporation High sensitivity fiber optic pressure sensor for use in harsh environments
US6024488A (en) * 1996-08-13 2000-02-15 National Science Council Highly accurate temperature sensor using two fiber Bragg gratings
US6097867A (en) * 1996-09-03 2000-08-01 The University Of New Mexico Technique for fabrication of a poled electro-optic fiber segment
US6139146A (en) * 1997-12-29 2000-10-31 Novartis Ag Programmable corrective lenses
US6139147A (en) * 1998-11-20 2000-10-31 Novartis Ag Actively controllable multifocal lens
US6185358B1 (en) 1996-12-03 2001-02-06 Samsung Electronics Co., Ltd. Optical attenuator and method of manufacturing same
US6215927B1 (en) 1998-05-26 2001-04-10 Minnesota Mining & Maufacturing Company Sensing tapes for strain and/or temperature sensing
US6330257B1 (en) 1998-08-06 2001-12-11 Sdl, Inc. Polarization-insensitive laser stabilization using multiple waveguide gratings
US6415078B1 (en) * 1995-04-17 2002-07-02 Sumitomo Electric Industries, Ltd. Laser light source and manufacturing method therefor
US20020093701A1 (en) * 2000-12-29 2002-07-18 Xiaoxiao Zhang Holographic multifocal lens
US6522797B1 (en) 1998-09-01 2003-02-18 Input/Output, Inc. Seismic optical acoustic recursive sensor system
US6580511B1 (en) * 1997-10-28 2003-06-17 Reliance Electric Technologies, Llc System for monitoring sealing wear
US20040264695A1 (en) * 2002-11-19 2004-12-30 Essex Corp. Private and secure optical communication system using an optical tapped delay line
US20080181553A1 (en) * 1997-10-28 2008-07-31 Reliance Electric Technologies, Llc System for monitoring sealing wear
US8135250B1 (en) * 2000-12-04 2012-03-13 Cirrex Systems Llc Facile production of optical communication assemblies and components
WO2016112422A1 (en) * 2015-01-14 2016-07-21 Adelaide Research & Innovation Pty Ltd Temperature sensor
DE102015217427A1 (en) * 2015-09-11 2017-03-16 Siemens Aktiengesellschaft Apparatus and method for identifying an optical waveguide
DE102016203007A1 (en) * 2016-02-25 2017-08-31 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Seal and method for sealing

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4398792A (en) * 1981-02-03 1983-08-16 The United States Of America As Represented By The Secretary Of The Air Force Holographic coupler for fiber optic systems
US4725110A (en) * 1984-08-13 1988-02-16 United Technologies Corporation Method for impressing gratings within fiber optics
US4761073A (en) * 1984-08-13 1988-08-02 United Technologies Corporation Distributed, spatially resolving optical fiber strain gauge
US4950883A (en) * 1988-12-27 1990-08-21 United Technologies Corporation Fiber optic sensor arrangement having reflective gratings responsive to particular wavelengths
US4996419A (en) * 1989-12-26 1991-02-26 United Technologies Corporation Distributed multiplexed optical fiber Bragg grating sensor arrangeement
US5237576A (en) * 1992-05-05 1993-08-17 At&T Bell Laboratories Article comprising an optical fiber laser
US5285274A (en) * 1991-04-26 1994-02-08 Pioneer Electronic Corporation Optical waveguide recording medium and apparatus for playing the same
US5295208A (en) * 1992-02-26 1994-03-15 The University Of Alabama In Huntsville Multimode waveguide holograms capable of using non-coherent light
US5295209A (en) * 1991-03-12 1994-03-15 General Instrument Corporation Spontaneous emission source having high spectral density at a desired wavelength

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4398792A (en) * 1981-02-03 1983-08-16 The United States Of America As Represented By The Secretary Of The Air Force Holographic coupler for fiber optic systems
US4725110A (en) * 1984-08-13 1988-02-16 United Technologies Corporation Method for impressing gratings within fiber optics
US4761073A (en) * 1984-08-13 1988-08-02 United Technologies Corporation Distributed, spatially resolving optical fiber strain gauge
US4807950A (en) * 1984-08-13 1989-02-28 United Technologies Corporation Method for impressing gratings within fiber optics
US4950883A (en) * 1988-12-27 1990-08-21 United Technologies Corporation Fiber optic sensor arrangement having reflective gratings responsive to particular wavelengths
US4996419A (en) * 1989-12-26 1991-02-26 United Technologies Corporation Distributed multiplexed optical fiber Bragg grating sensor arrangeement
US5295209A (en) * 1991-03-12 1994-03-15 General Instrument Corporation Spontaneous emission source having high spectral density at a desired wavelength
US5285274A (en) * 1991-04-26 1994-02-08 Pioneer Electronic Corporation Optical waveguide recording medium and apparatus for playing the same
US5295208A (en) * 1992-02-26 1994-03-15 The University Of Alabama In Huntsville Multimode waveguide holograms capable of using non-coherent light
US5237576A (en) * 1992-05-05 1993-08-17 At&T Bell Laboratories Article comprising an optical fiber laser

Cited By (43)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5471551A (en) * 1991-12-24 1995-11-28 Robert Bosch Gmbh Component for use in the transmission of optical signals
US5416866A (en) * 1992-08-26 1995-05-16 Telefonaktiebolaget L M Ericsson Optical waveguide/grating device for filtering optical wavelengths
US5625472A (en) * 1992-12-23 1997-04-29 Lucent Technologies Inc. Method for forming distributed Bragg reflectors in optical media
US5475780A (en) * 1993-06-17 1995-12-12 At&T Corp. Optical waveguiding component comprising a band-pass filter
US5457760A (en) * 1994-05-06 1995-10-10 At&T Ipm Corp. Wavelength division optical multiplexing elements
WO1996017223A1 (en) * 1994-11-29 1996-06-06 United Technologies Corporation Optical fiber bragg grating coating removal detection
US5493113A (en) * 1994-11-29 1996-02-20 United Technologies Corporation Highly sensitive optical fiber cavity coating removal detection
US6885785B2 (en) 1994-11-29 2005-04-26 United Technologies Corporation Optical fiber bragg grating coating removal detection
US20030118297A1 (en) * 1994-11-29 2003-06-26 Dunphy James R. Optical fiber Bragg grating coating removal detection
US20050018945A1 (en) * 1994-11-29 2005-01-27 Dunphy James R. Optical fiber bragg grating coating removal detection
WO1996031022A1 (en) * 1995-03-27 1996-10-03 Bicc Public Limited Company Optical fibre and network
US6415078B1 (en) * 1995-04-17 2002-07-02 Sumitomo Electric Industries, Ltd. Laser light source and manufacturing method therefor
US5633975A (en) * 1995-11-14 1997-05-27 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Security system responsive to optical fiber having Bragg grating
US5892869A (en) * 1996-06-24 1999-04-06 Trw Inc. Optical-loop signal processing using reflection mechanisms
US5838851A (en) * 1996-06-24 1998-11-17 Trw Inc. Optical-loop signal processing using reflection mechanisms
US5903691A (en) * 1996-06-24 1999-05-11 Trw Inc. Optical-loop signal processing using reflection mechanisms
US5896476A (en) * 1996-06-24 1999-04-20 Trw Inc. Optical loop signal processing using reflection mechanisms
US5760391A (en) * 1996-07-17 1998-06-02 Mechanical Technology, Inc. Passive optical wavelength analyzer with a passive nonuniform optical grating
US6024488A (en) * 1996-08-13 2000-02-15 National Science Council Highly accurate temperature sensor using two fiber Bragg gratings
US6097867A (en) * 1996-09-03 2000-08-01 The University Of New Mexico Technique for fabrication of a poled electro-optic fiber segment
US6185358B1 (en) 1996-12-03 2001-02-06 Samsung Electronics Co., Ltd. Optical attenuator and method of manufacturing same
US5892860A (en) * 1997-01-21 1999-04-06 Cidra Corporation Multi-parameter fiber optic sensor for use in harsh environments
US5852687A (en) * 1997-07-09 1998-12-22 Trw Inc. Integrated optical time delay unit
US6016702A (en) * 1997-09-08 2000-01-25 Cidra Corporation High sensitivity fiber optic pressure sensor for use in harsh environments
US7551268B2 (en) 1997-10-28 2009-06-23 Rockwell Automation Technologies, Inc. System for monitoring sealing wear
US20080181553A1 (en) * 1997-10-28 2008-07-31 Reliance Electric Technologies, Llc System for monitoring sealing wear
US6580511B1 (en) * 1997-10-28 2003-06-17 Reliance Electric Technologies, Llc System for monitoring sealing wear
US6139146A (en) * 1997-12-29 2000-10-31 Novartis Ag Programmable corrective lenses
US5997140A (en) * 1997-12-29 1999-12-07 Novartis Ag Actively controllable multifocal lens
US6215927B1 (en) 1998-05-26 2001-04-10 Minnesota Mining & Maufacturing Company Sensing tapes for strain and/or temperature sensing
US6385377B1 (en) * 1998-08-03 2002-05-07 University Of New Mexico Technique for fabrication of a poled electro-optic fiber segment
US6330257B1 (en) 1998-08-06 2001-12-11 Sdl, Inc. Polarization-insensitive laser stabilization using multiple waveguide gratings
US6522797B1 (en) 1998-09-01 2003-02-18 Input/Output, Inc. Seismic optical acoustic recursive sensor system
US6139147A (en) * 1998-11-20 2000-10-31 Novartis Ag Actively controllable multifocal lens
US8363992B1 (en) * 2000-12-04 2013-01-29 Cirrex Systems Llc Facile optical assemblies and components
US8135250B1 (en) * 2000-12-04 2012-03-13 Cirrex Systems Llc Facile production of optical communication assemblies and components
US20020093701A1 (en) * 2000-12-29 2002-07-18 Xiaoxiao Zhang Holographic multifocal lens
US7720226B2 (en) 2002-11-19 2010-05-18 Essex Corporation Private and secure optical communication system using an optical tapped delay line
US20040264695A1 (en) * 2002-11-19 2004-12-30 Essex Corp. Private and secure optical communication system using an optical tapped delay line
WO2016112422A1 (en) * 2015-01-14 2016-07-21 Adelaide Research & Innovation Pty Ltd Temperature sensor
DE102015217427A1 (en) * 2015-09-11 2017-03-16 Siemens Aktiengesellschaft Apparatus and method for identifying an optical waveguide
DE102016203007A1 (en) * 2016-02-25 2017-08-31 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Seal and method for sealing
WO2017144405A1 (en) * 2016-02-25 2017-08-31 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Seal and sealing method

Similar Documents

Publication Publication Date Title
Yin et al. Fiber optic sensors
Hill et al. Bragg gratings fabricated in monomode photosensitive optical fiber by UV exposure through a phase mask
Erdogan et al. Characterization of UV-induced birefringence in photosensitive Ge-doped silica optical fibers
US6545808B1 (en) Phase mask with spatially variable diffraction efficiency
US5491570A (en) Methods and devices for using photorefractive materials at infrared wavelengths
US6067391A (en) Multiply periodic refractive index modulated optical filters
US4006967A (en) Directing optical beam
US6151142A (en) Grazing incidence holograms and system and method for producing the same
Marshall et al. Point-by-point written fiber-Bragg gratings and their application in complex grating designs
US5946429A (en) Time-division multiplexing of polarization-insensitive fiber optic michelson interferometric sensor
US6404956B1 (en) Long-length continuous phase Bragg reflectors in optical media
EP0376449A1 (en) Interferometer
Azaña et al. Real-time optical spectrum analysis based on the time-space duality in chirped fiber gratings
US5016967A (en) Multi-core optical waveguide Bragg grating light redirecting arrangement
US5263039A (en) System for generating shaped optical pulses and measuring optical pulses using spectral beam deflection (SBD)
US5822479A (en) Writing diffraction gratings with interference fringe patterns
US4895421A (en) Dynamic couplers using two-mode optical waveguides
US5550654A (en) Method for forming, in optical media, refractive index perturbations having reduced birefringence
McCall On the application of coupled mode theory for modeling fiber Bragg gratings
US5848204A (en) Fiber devices and sensors based on multimode fiber Bragg gratings
Yin et al. Wavelength multiplexed holographic storage in a sensitive photorefractive crystal using a visible-light tunable diode laser
US6621960B2 (en) Method of fabricating multiple superimposed fiber Bragg gratings
Lambelet et al. Bragg grating characterization by optical low-coherence reflectometry
US5241616A (en) Optical pattern recognition system utilizing resonator array
US7046866B2 (en) System and method for fabricating Bragg gratings with overlapping exposures

Legal Events

Date Code Title Description
AS Assignment

Owner name: REGENTS OF THE UNIVERSITY OF CALIFORNIA, THE, NEW

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:FORMAN, PETER R.;REEL/FRAME:006715/0787

Effective date: 19930909

AS Assignment

Owner name: ENERGY, DEPARTMENT, UNITED STATES, DISTRICT OF COL

Free format text: CONFIRMATORY LICENSE;ASSIGNOR:CALIFORNIA, UNIVERSITY OF;REEL/FRAME:007742/0205

Effective date: 19931110

FPAY Fee payment

Year of fee payment: 4

FPAY Fee payment

Year of fee payment: 8

REMI Maintenance fee reminder mailed
AS Assignment

Owner name: LOS ALAMOS NATIONAL SECURITY, LLC, NEW MEXICO

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:REGENTS OF THE UNIVERSITY OF CALIFORNIA, THE;REEL/FRAME:017897/0897

Effective date: 20060417

LAPS Lapse for failure to pay maintenance fees
FP Expired due to failure to pay maintenance fee

Effective date: 20060927